GB2178101 discloses a tether anchor arrangement comprising a socket body and an plug body, as shown in FIG. 1, wherein each body is provided with radially extending, load bearing projections. In use, as the plug body is inserted into the socket body, radially extending tabs provided on the socket body engage into guide channels recessed in the plug body which effect relative rotation between the bodies as they are interengaged so as to bring the radially extending projections into axial alignment in the manner of a bayonet coupling. Subsequently, upon tensioning of the tether, the plug body is raised in the socket body, whereupon the tabs and channels co-operate to guide the axially aligned projections into abutment such that the plug is locked in the body. Upon release of tension the plug body drops back into the socket body, whereupon the followers and cams co-operate again to rotate the bodies relative to each other, this time such that the radially extending projections on the bodies can once more pass between each other, thus facilitating disconnection.
Such known connector assemblies have a drawback, however, in that, in use, they can become disconnected upon a temporary drop in the tension in the tether. In particular, this is widely known to be problematic in applications such as connecting tendon strings to anchor templates in tether systems for tethered leg platforms, wherein members can occasionally become un-tensioned during use due to alternating sea water forces acting thereon.
It is an object of the present invention to provide a connector assembly that, in use, cannot become undesirably disconnected upon an incidental release in tension.
According to a first aspect of the present invention there is provided a releasable connector assembly comprising:
a socket member having a substantially cylindrical receptacle formed therein which includes at least one load bearing projection; and
a plug member including at least one load bearing projection;
one of the socket member and the plug member having at least one channel formed therein and the other of the socket member and the plug member having at least one radial tab formed thereon, the or each channel forming a keyway for the or each tab, and the or each load bearing projection of the members being releasably engageable in the manner of a bayonet coupling such that, in a first angular position, they are axially misaligned to allow insertion or removal of the plug from the socket, and in a second angular position, they are axially aligned to prevent removal of the plug from the socket;the or each channel including a first and second passageway, a first camming surface which extends circumferentially and axially, a second camming surface which extends axially in the opposite direction to and circumferentially away from the first camming surface to a blind undercut, and a third camming surface which extends axially in the same direction as the first camming surface and circumferentially away from the second camming surface;wherein, upon insertion of the plug member into the socket member with the or each load bearing projection of the members arranged in the first angular position, the at least one tab enters the at least one channel via the first passageway and, engages with the first camming surface, the camming action thereof causing relative rotation between the members as the plug is inserted into the socket so that when the plug is fully inserted into the socket, the tab underlies the second camming surface;upon subsequent raising of the plug from the socket, the tab engages with the second camming surface, the resulting camming action continuing the plug further to rotate relative to the socket, guiding the tab into the undercut such that the or each load bearing projection of the members are arranged in the second angular position so as to prevent removal of the plug from the socket with any tension on the plug member being transmitted to the socket through the or each projection;and wherein re-lowering of the plug into the socket brings the tab into engagement with the third camming surface, the resulting camming action continuing the relative rotation between the plug and socket so as to bring the tab into alignment with the second passageway and to move the or each load bearing projection of the members back towards their first angular position, whereupon the plug may be completely removed from the socket;characterised in that at least one moveable locking pin is provided in the one of the socket member and the plug member, the or each pin being extendable into the or each channel so as, in use, to trap the tab in the undercut, thereby preventing unintentional release of the plug from the socket, and being retractable from the or each channel so as to enable release of the plug from the socket.
In an alternative aspect, the or each channel forms a keyway for at least one pair of tabs, wherein:
upon insertion of the plug member into the socket member with the or each load bearing projection of the members arranged in the first angular position, a first and second tab of the or each pair of tabs enter the or each channel, via the first and second passageways respectively, such that the second tab of the or each pair engages with the first camming surface, the camming action thereof causing relative rotation between the members as the plug is inserted into the socket so that when the plug is fully inserted into the socket, the first tab of the or each pair underlies the second camming surface;upon subsequent raising of the plug from the socket, the first tab of the or each pair engages with the second camming surface, the resulting camming action continuing the plug to rotate further relative to the socket, guiding said first tab of the or each pair into the undercut such that the or each load bearing projection of the members are arranged in the second angular position;and wherein re-lowering of the plug into the socket brings the first tab of the or each pair of tabs into engagement with the third camming surface, the resulting camming action continuing the relative rotation between the plug and socket so as to bring said first tab into alignment with the second passageway and the second tab of the at least one pair into alignment with a further passageway, and to move the or each load bearing projection of the members back towards their first angular position, whereupon the plug may be completely removed from the socket.
A connector assembly in accordance with the present invention has the advantage that the locking pin prevents the plug from dropping back into the socket, thereby preventing unintentional release of the connector, whilst any upward load applied to the plug is carried by the load bearing projections. As a result, the pin only carries the weight of the plug and any tether attached thereto and hence does not need to be especially strong, and the resulting system is therefore very reliable and robust. Furthermore, it also provides a particularly cost effective construction.
Desirably, the or each locking pin and the or each channel are provided on the socket member whilst the or each tab is provided on the plug member. However, the opposite configuration is also possible.
Preferably, the or each axially extending undercut, tab and locking pin are arranged such that, in use, there is axial play between the or each tab and the or each locking pin. In this way, the plug member can advantageously drop down slightly before contacting the or each locking pin. Desirably, the axial play is substantially 1.0 m.
In an advantageous development, the or each locking pin, in a first position, extends from the other said member via at least one vent hole provided therein. Furthermore, the first position of the at least one locking pin is such that it advantageously directly traps the tab in the undercut, preferably by extending into the mouth of the undercut. Alternatively, however, the first position of the at least one locking pin is such that it indirectly traps the tab in the undercut, desirably by blocking the movement of a base on which the at least one tab is mounted.
Preferably, the or each locking pin, or alternatively an activation means thereof, is accessible from an outer surface of the one of the socket member and plug member such that it is remotely operable between its extended and retracted positions. In particular, the or each locking pin is desirably operable via remotely operated vehicle (ROV). However, it will be appreciated that the or each locking pin could alternatively be operable via a server motor or any other known means.
Advantageously, the socket body is provided with a plurality of equally angularly spaced load bearing projections that co-operate with complementary load bearing projections provided on the plug body. Furthermore, a plurality of equally angularly spaced channels are likewise preferably provided on one of the bodies, which desirably co-operate with a complementary number of tabs, whereby the channels are preferably linked together such that the tabs rotate from one channel to another as the connector is engaged and disengaged, each entry portion for one channel also operating as the exit portion for the preceding channel. A locking pin is then advantageously associated with the blind undercut of each channel, although it will be understood that the number of locking pins and channels provided may be varied depending on the particular circumstances and design of the connector assembly.
In one development, the or each channel comprises first, second and third camming surfaces only. Accordingly, during engagement, the or each locking pin is desirably retracted from the or each channel so as to allow the or each tab to rise into the or each undercut, the or each locking pin subsequently being extended into the or each channel ready for use. In this way, the tab is advantageously guided into the undercut via a simple camming system. However, during engagement, the or each locking pin is alternatively biased to extend into the or each channel by at least one spring and is provided with a camming surface such that it automatically retracts when engaged by the or each associated tab as it rises into the or each undercut. In this way, effective locking of the plug in the socket is ensured without the need to actively operate the or each locking pin. Either way, the pin has to be actively retracted to allow release.
In an alternative development, the or each channel includes at least one further camming surface such that the or each locking pin can advantageously be extended during engagement. In particular, a the or each fourth camming surface preferably extends axially in the same direction and circumferentially towards the or each first camming surface such that, whilst the plug is being raised from the socket during engagement, the or each second camming surface guides the or each tab under the or each locking pin and undercut and into engagement with the or each fourth camming surface, the resulting camming action rotating the plug relative to the socket in a reverse sense and guiding the or each tab over the or each locking pin and into the or each undercut. In this way, effective locking of the plug in the socket is again ensured without the need to actively operate the or each locking pin, although it does have to be actively retracted to allow release.